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Bloat In Young Calves & Other Pre-ruminant Livestock

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Developed by Rob Costello
Technical Specialist 
Bloat results from a variety of factors, but the common thread throughout all bloat cases is production of gas by organisms in the digestive tract. Feed equipment, feed temperature, feed ingredients, amount fed, feeding frequency, water availability, weather, stress etc., may be involved, but they do not cause bloat by themselves. Organisms, and not necessarily the pathogenic ones, produce the gas that causes bloat.
Susceptibility of individual animals to bloat is variable and genetics may play a part in some cases. Bloat can be a chronic problem on some farms and never occur on others. Although working through a bloat problem can be truly frustrating, many factors can be controlled to prevent bloat or to at least minimize its occurrence. 
Rumen Development - changes in digestive function and structure: 
The pre-ruminant stomach is made up of the same four structures or compartments as the adult ruminant stomach. At birth, the abomasum is the dominant structure while the rumen is basically non functional. As the calf consumes various feeds and water, its rumen gradually develops and increases in size and digestive function. Bloat can affect either the abomasum or the rumen.

Abomasal bloat. The abomasum of an affected calf usually becomes grossly distended within 1hour after feeding with death occurring within a few minutes after the distention becomes clinically obvious -- along the right side of the animal. Treatment of abomasal bloat is very difficult. Factors contributing to abomasal bloat include overfeeding milk or feeding milk too fast.  In the presence of fermenting bacteria, a large quantity of milk or milk replacer arriving at the abomasum can provide an excellent substrate for these bacteria to grow rapidly and ferment sugars. Excessive gas is produced as a result of this rapid fermentation. The end result is overproduction of gas that cannot escape.
Overeating or abrupt diet changes tend to produce indigestion that slows gut movement, providing the sugars, proteins and lack of oxygen needed for rapid growth of many bacteria, such as Clostridium. Clostridium perfringens Type A causes stomach irritation and can lead to abomasal ulcers and bloat. Affected calves may stop eating, show uneasiness and strain or kick at their abdomen. Calves are often found dead without having shown any previous symptoms. Moderate bloating of the abomasum is often found.
Sarcina bacteria have been reported in association with abomasal bloat in lambs and to a lesser extent with calves. The presence of sarcina in the digestive tract is not unusual, but in these bloat cases it multiplies very rapidly causing reddish areas or abscesses to form in the abomasum, leading to weakness in the stomach wall. It is unlear whether this organisms causes bloat or is an merely an opportunist that grows rapidly under bloat conditions 
Ruminal bloat. Ruminal bloat occurs when gas produced during rumen fermentation builds up in the rumen and is unable to escape. Normal rumen contractions decrease and belching becomes impossible, preventing gas from being expelled. As gas accumulates, abdominal swelling can be observed behind the rib cage on the left flank. Ruminal bloat can become live threatening within a few hours and usually requires medical attention. 
Ruminal bloat in young calves takes place within the context of the developing rumen. The size and make-up of the population of rumen microbes at any point in time is determined by the types of feed consumed as well as other substances commonly ingested such as bedding and hair. The right set of circumstances can allow one or more of these microbes to produce excessive gas and bloat in the developing rumen.  
The amount and quality of water provided and the microbial population it contains can have significant effects on rumen development and function. The general recommendation is to feed four pounds of water (2 qt) for every pound of dry feed consumed. Under the right set of circumstances, management practices that slow or impede rumen development can set the stage for bloat and other digestive problems. 
Management factors that can influence to incidence of bloat:
  • colostrum management
  • feeding time
  • milk temperature
  • feeding equipment
  • antibiotics
  • feed ingredients
  • stress
  • health status 
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